Cigarette Smoking has been decribed as the most significant preventable cause of premature death and disability in industrialized countries. Smoking is a proven risk factor for the three leading causes of death in the United States: heart disease, malignant neoplasms, and stroke. It is estimated that smoking is causally related to some 225,000 deaths due to cardiovascular disease, 80,000 deaths from lung cancer, 22,000 deaths from other cancers, and more than 19,000 deaths from pulmonary disease annually in the U.S. alone. Although considerable media attention has been devoted to the health consequences of smoking (U.S.P.H.S., 1982), appoximately one-third of adults continue to smoke. While posttreatment cessation rates have risen somewhat over the past decade, up to 80% of smokers who initially stop smoking will relapse within a very short period of time. One neglected variable in the smoking relapse area is weight gain following smoking cessation. Recent surveys indicate that 1/3 of all smokers (39% of female smokers and 25% of male smokers) report that they smoke in order to regulate their body weight. Despite the obvious relationship between smoking and weight gain, very little is known regarding the reasons for weight gain following smoking cessation. There is recent evidence that the predictors of weight gain may be different in men than in women. Thus, the goals of this project are threefold. First, we intend to determine, in a comprehensive fashion, the determinants (i.e., food intake, physical activity, changes in metabolic rate) of weight gain following smoking cessation in a biracial sample of 800 adult males and females. Our second goal is to determine who (i.e., Blacks vs Whites; males vs females) is most at risk for potential weight gain and relapse. Our final goal is to determine if weight gain following smoking cessation predicts relapse in a prospective, multiple assessment design. The outcomes of this research will have extremely important implications for future intervention efforts.